358 PHYSIOLOGICAL CHEMISTBY. 



according to the method suggested by NEUBAUER, who treats 

 500-600 c. c. of the urine with CaCl 2 solution, makes alkaline with 

 ammonia and then faintly acid with acetic acid. After 24 hours 

 the precipitate is collected on a small filter, washed with water, 

 treated with hydrochloric acid (which leaves the uric acid undis- 

 solved on the filter), and washed again with water. The filtrate, 

 including the wash- water, is treated with an excess of ammonia and 

 allowed to stand 24 hours. Calcium oxalate separates as quadratic 

 octahedra. The quantitative estimation is performed after the 

 same principle. The oxalate is converted into quick-lime by heat, 

 and weighed as such. 



Allantoin or GLYOXYLDIUEEID, C 4 H 6 N 4 3 or 



,^/NH.CH.NH.CO.NH, 



C0< ^TT pr\ > occurs in the urine of children within 



the first eight days after birth, and in very small amounts also in 

 the urine of grown persons (GussEROW, ZIEGLEB and HERMANN). 

 It is found in rather abundant quantities in the urine of pregnant 

 women (GUSSEROW). Allantoin has also been found in the urine 

 of sucking calves (WOHLER), and sometimes in the urine of other 

 animals (MEISSKER). It is also found in the amniotic fluid and 

 allantoic fluid of the cow (hence the name). Allantoin is formed, 

 as above stated, by the oxidation of uric acid. The increased elim- 

 ination of allantoin which SALKOWSKI observed in dogs after the 

 administration of uric acid shows that the formation of allantoin 

 from uric acid in the organism is not improbable. 



Allantoin is a colorless substance often crystallizing in prisms, 

 difficultly soluble in cold water, easily soluble in boiling water and 

 also in warm alcohol, but not soluble in cold alcohol or ether. It 

 combines with acids, forming salts. A watery allantoin solution 

 gives no precipitate with silver nitrate alone, but by the careful 

 addition of ammonia a white flocculent precipitate is formed, 

 C 4 H 5 AgN 4 3 , which is soluble in an excess of ammonia and which 

 consists after a certain time of very small, transparent microscopic 

 globules. The dried precipitate contains 40.75$ silver. A watery 

 allantoin solution is precipitated by mercuric nitrate. 



Allantoin is most easily prepared by the oxidation of uric acid 

 with lead peroxide. In preparing allantoin from calves' urine, con- 

 centrate the urine on the water-bath to a syrup and allow it to 

 stand in the cold for several days. The crystals which are sepa- 



